1. Field of the Invention
The present invention relates to a liquid storage tank for storing a supply of liquid received under a comparatively high pressure and for dispensing the same in such a way that the liquid is discharged at a small and constant flow rate under atmospheric pressure or a similar pressure condition.
2. Description of the Prior Art
For continuous discharge, including intermittently continuous discharge, of liquid under a required pressure and flow rate from an incoming supply of the same under pressure, a large-type liquid storage tank is generally employed as, for example, in a cistern for a flush toilet, wherein water is stored for periodic discharge in large quantities, or in an elevated water-service tank installed on a building roof or at a like location, wherein water is stored after being pumped up.
In these storage tanks, liquid is normally stored at a constant level through a automatic supply of the same into the tank as required, and for this purpose a float valve is employed such that liquid supply is automatically stopped when a target liquid level is reached. The manner of liquid level control by a float valve will be explained in detail hereinbelow. In the following description, the liquid involved is understood to be water.
In conventional liquid storage tanks, a float valve 4 as shown in FIG. 6 or FIG. 7 is employed, whereby water supply is controlled so that a predetermined quantity of water is constantly stored in a tank body 1. A feed pipe 5' is connected to a sidewall of the tank body 1 at a position higher than the target water level. The feed pipe 5' is fitted with a float valve 4 which serves to open and close the mouth of the feed pipe 5' as a float member 8 moves upward and downward with changes in the water level in the tank. Any float valve 4 must input a sufficient water stopping force for closing the mouth of the feed pipe 5' against a feed water pressure which is normally on the order of 3 kg/cm.sup.2 -5 kg/cm.sup.2. In the case of the float valve of the ball-tap type as shown in FIG. 6, a moment of force resulting from a combination of a large degree of buoyancy provided by the float member 8 and an elongated arm member 9' is utilized to provide a sufficiently magnified force for closing the mouth of the feed pipe against the feed water pressure. In the case of the float valve as shown in FIG. 7, a large float member 8 is employed which is of an internally hollow construction or which is constructed of a material having a much lower density than water, in order to provide sufficient buoyancy to produce a force large enough to counteract the feed water pressure.
Any such conventional liquid storage tank as described above is designed primarily for storing a large quantity of liquid therein. In the above-described prior art, no proposal has been made oriented toward rendering such a tank or float valve component thereof smaller, although in the areas where large-type storage tanks are required, there is no particular need for rendering the tanks smaller. Since the liquid feed stopping mechanism employing a float valve is for stopping liquid feed against the feed liquid pressure involved, a large-size float member and a considerably long arm member are required to provide a sufficient water stopping force that can overcome the pressure, which necessarily results in a large-size construction for the float valve.
However, in the cas of supplying water to a humidifier, for example, it is required that the water supplied under pressure must be first stored in a tank and subsequently released from the tank intermittently, continuously and steadily in predetermined small quantities under atmospheric pressure. If the humidifier itself is not relatively large and if a storage tank for supplying water under such conditions is to be incorporated in the humidifier, a small-size storage tank is required. Needless to say, it is unjustifiable and undesirable to employ a float valve of the conventional type described above in such small-size storage tanks. However, it is also unjustifiable to use a high-performance regulator, valve, or the like for control purposes, because it involves a great deal of complexity with respect to the control mechanism and a high cost of equipment.